The present invention concerns a method for equalizing the density distribution of pressed wood panels manufactured from adhesive coated bulk material and apparatus for accomplishing same.
In the manufacture of pressed wood panels, there is a great economical interest in producing chip material that is spread as evenly as possible, since it is possible only in this manner to ascertain that the properties of the finished pressed wood panels, such as density, bending strength, and transverse tensile strength, for example, are uniform at all points of the end product. Excess quantities of bulk material, adhesive, and energy are thereby eliminated. According to DE-PS No. 22 14 900, which concerns a spreading device for the purpose of equalizing weight variations per surface unit in the lateral direction of chip, fiber or similar material in the manufacture of particle or fiberboard panels, a device is known whereby a feed conveyor belt is used in order to distribute bulk material as chip material to be deposited on a form base. In order to equalize different weights per surface unit in the lateral direction of chip or fiber material, the provision is made that the feed conveyor belt can be adjusted to different elevations, continuously and in the lateral direction. Additional devices of this nature are not appropriate for detection and elimination of variations in the weight per surface unit in the lateral direction of the chip or fiber material, i.e. of the pressed wood panels, as early as in the stage of creating a bulk material stream. Nor is it possible, in this manner, to determine the varying density in the lateral direction of the feed conveyor belt.
A pass-through procedure is known from DE-PS No. 25 57 352 for continuous spreading of particle material of wood chips and/or fibers, consisting of several layers spread separately, the surface weight of which is adjusted to a predetermined nominal value, where the weight of the fully spread particle material is measured and indicated, and whereby corresponding electrical measurement signals control the spreading of at least one layer of particle material to a preset nominal value of the completely spread material. However, in this case, it is similarly impossible to equalize the density distribution in the transverse direction of the particle material. Furthermore, scales for surface weight are known (cf. Wood as Raw Material and Fabrication Material 40 (1932), p. 385), whereby the distribution of weight per surface unit in the spread-out wood chip material is determined by means of radiometric methods and devices traversing the material along and across the production direction.